Since the intention has been to 3D print the models I was going to make with SketchUp, I started discussing 3D Printing with the University of Waterloo’s 3D Print Center. I attached my in-progress file for the operator there to take a look at it, when I got the news.

My file wouldn’t print properly.

I re-opened the .skp file I was working in, and made a few modifications around the parts the operator indicated were causing problems. I sent back the modified file.

Same thing, different places.

Clearly this is a huge problem, what’s the point of making a 3D printable model that can’t 3D print!? So, deep breath, take a step back, and tell yourself, “alright, I’m not doing something right.” Then, ask  “what am I doing wrong, or how can I do it right?” So, off to Google I go, and find a very helpful site, that I really should have read before I started anything: http://www.mastersketchup.com/8-tips-for-3d-printing-with-sketchup/

So in an attempt to summarize some of that, here are the biggest take aways for me:

SketchUp Extensions

I recently did a presentation on my project and one of the aspects of SketchUp I praised was the ability to extend the base capabilities. There is one that is pretty much essential to 3D printing with SketchUp.

SketchUp STL

The .stl file extension is the most widely used file format for 3D printing, so being able to save your model in a format that is understood by 3D printing software and hardware is essential. This extension just includes an option to export and import .stl files of your 3D model. This is what I used to send files to the 3D Printing Operator.

Solid Inspector

This extension adds a mode that highlights problematic edges and areas in your model, and gives you a guideline of what to do to make it “solid”, which is necessary for your model to 3D print properly. If it’s not solid due to internal faces or geometry, this could potentially cause the 3D print to interpret your file in strange ways. What was happening with my files in particular was that sections would be printed in the support material that would eventually get dissolved, instead of the normal plastic. This would have caused problems with the final piece.

Back to Basics

On top of all this, the way I was constructing my model was really incorrect. Sure, it looked good on the surface, but as our mothers and PSAs have told us, it’s what’s on the inside that matters. To finally get my file in a state that could be printed properly, I went back to basics and built it all over, but this time using groups.

Groups

When you select a group of edges or faces, you can right click, and you’ll find an option to “Make a Group”. (Protip: Triple click to select all faces and edges that are touched by a piece of geometry) The advantage of groups is that when you move them, even if you intersect any edges or faces on the outside, it leaves the group untouched. If your selected geometry isn’t grouped, then SketchUp tries to intelligently intersect and merge the shapes. This sounds great in theory, but computers still aren’t really good at the whole “original thought” thing, and can result in things you don’t want. Plus, after it happens it’s a pain to move it again without moving a bunch of other pieces in the model.

Solid GRoups

An example of a Solid Group

An example of a Solid Group

Just groups alone make it a lot easier to work in SketchUp, but what is this solid business? As outlined above, an object needs to be “solid” to be 3D printed. In SketchUp, if you enable to Entity Info window (Window-> Entity Info) clicking on a group will immediately tell you whether it’s solid or not.

Once all your groups are solid and arranged how you want them, you should be able to export to STL, and you should be ready to print!

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